1. Field of the Invention
The present invention relates to an improved process for the production of C.sub.2.sup.+ hydrocarbons, especially those boiling in the gasoline range, from feed materials containing methane. In particular, the invention provides a process for converting a methane containing feed in an oxidative conversion reaction to a mixture comprised of ethylene, hydrogen, carbon oxides, and unreacted methane, and thereafter converting this mixture to higher hydrocarbons in improved yields by reaction over a dual catalyst which promotes both hydrogen and carbon monoxide reaction and ethylene oligomerization.
2. Description of the Prior Art
Large quantities of natural gas, which is primarily methane, are found at remote sites. Because of transportation difficulties and expense, this natural gas is largely unused.
A great deal of effort and expense has gone into research programs designed to provide improved methods for the conversion of methane (natural gas) to higher boiling hydrocarbons, i.e. C.sub.2.sup.+ hydrocarbons, which can more readily be transported from remote locations to those locations where the higher hydrocarbons can be used.
In particular, the oxidative conversion of methane to higher hydrocarbons has been the subject of extensive efforts. Both "cofeed" and "redox" mode operations have been studied; cofeed systems being those in which a mixture of methane and gaseous oxidant are contacted at reactive conditions with a solid contact agent, and redox systems being those wherein a solid contact agent comprised of reducible metal oxide is alternately contacted at reaction conditions with methane and with gaseous oxidant. Patents relating to these technologies include the following U.S. Pat. Nos. 4,443,649, 4,444,984, 4,443,648, 4,443,645, 4,443,647, 4,443,644, 4,443,646, 4,449,323, 4,499,324, 4,593,139, 4,489,215, 4,499,322, 4,495,374, 4,544,784, 4,544,785, 4,547,610, 4,547,611, 4,517,398, 4,544,787, 4,547,608, 4,544,786, 4,568,785, 4,629,718, 4,650,781, 4,554,395, 4,560,821, 4,547,607, 4,533,780, 4,523,049, 4,523,050, 4,634,800, 4,608,449, and the like.
In U.S. Pat. No. 4,567,307, above mentioned, there is described a process wherein methane is contacted at reactive conditions with a reducible metal oxide to produce ethylene, and the ethylene is oligomerized to produce higher hydrocarbon products. This patent provides a comprehensive listing of pertinent references showing catalysts, especially shape selective crystalline molecular sieve materials, which are useful to catalyze the ethylene oligomerization.
In PCT International Publication No. WO 86/05176 published Sept. 12, 1986 there is described a process wherein methane in admixture with oxygen is reacted over an oxidative coupling catalyst to produce a product mixture comprised of higher hydrocarbons and this mixture is contacted with an oligomerization catalyst under aromatization conditions to produce a mixture of aromatic hydrocarbon and saturated aliphatic hydrocarbons of higher molecular weight than methane.
Considerable prior art exists which relates to the conversion of synthesis gas, i.e. carbon oxides and hydrogen, to hydrocarbons. See, for example, European publication No. 0,099,715 of British Petroleum, U.S. Pat. No. 4,659,743, Ind. Eng. Chem. Res., 1987, Vol 26, pages 183-188, U.S. Pat. No. 4,487,851, Journal of Catalysis, Vol. 107, pages 471-481 (1987), and the like.
Considerable work in the area of conversion of mixtures of ethylene, hydrogen, and carbon monoxide to higher hydrocarbons has been reported by Russian workers. See, for example, the following: Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 4, pp. 772-778, April 1967, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 5, pp. 1016-1023, May 1967, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 5, pp. 1059-1065, May 1969, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 7, pp. 1472-1477, July 1971, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 7, pp. 1470-1476, July 1967, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 10, pp. 1812-1817, October 1966, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 8, pp. 1710-1714, August 1967, Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 6, pp. 1257-1262, June 1967, and Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 12, pp. 2719-2725, December 1971.
Also, in U.S. Pat. No. 4,487,984 there is described the alkylation of an aromatic compound by reacting the aromatic compound with a mixture of carbon monoxide and hydrogen at alkylation conditions with a dual-function catalyst. The catlayst is described as being comprised of (1) a composite of oxides of copper, zinc and aluminum or chromium and (2) an alumino silicate which may be either in crystalline or amorphous form.